Magnetoresistive device and barrier formation process

ABSTRACT

A magnetoresistive (MR) device and barrier formation process is disclosed in which a barrier layer of an aluminum-titanium oxidic compound of approximately 35 Å thickness is formed between a first alumina film and an overlying material of iron bearing content, such as nickel-iron. The aluminum-titanium oxidic compound layer serves as an etchant barrier for the alumina film in a subsequent etching process to reduce or eliminate &#34;rosette&#34; formation otherwise occurring when etchant is trapped within pores of a porous substrate such as ferrite, ceramic or other polycrystalline material. The barrier layer also serves as a passivation layer to prevent the surface of the underlying alumina film from being modified by the transfer of ultrasonic energy during subsequent wirebonding processing which would otherwise result in film delamination at the nickel-iron/alumina layer interface.

This is a divisional of application Ser. No. 08/022,679, filed on Mar.1, 1993, now U.S. Pat. No. 5,350,629.

BACKGROUND OF THE INVENTION

The present invention relates to improvements in magnetoresistive (MR)devices and methods for fabricating the same. More particularly, the MRdevice and the method of fabricating it are of particular utility in themanufacture of MR read heads of the non-shunt bias type for use incomputer mass storage devices. Even more particularly the presentinvention provides a barrier layer to substantially obviate the priorsignificant problems of film delamination and "rosette" formation duringfabrication of MR devices.

The design of a shunt biased magnetic head for use in magnetic tapesubsystems utilizing magnetoresistive read elements is generallydescribed in Cannon et al., "Design and Performance of a Magnetic Headfor a High-Density Tape Drive", IBM J. Res. Develop., Vol. 30, No. 3 May1986, the disclosure of which is hereby specifically incorporated byreference. In the formation of MR heads of the non-shunt bias type, afirst alumina (Al₂ O₃ -aluminum oxide) layer is generally sputterdeposited on a ferrite substrate. A nickel iron (NiFe) film and atitanium (Ti) overcoat are then deposited on the alumina layer.Utilizing photolithographic techniques, appropriate device dimensionsare photo-defined and the structure is then ion-milled to define thehead tracks. Following this step, a gap layer comprising a second layerof alumina is deposited, photo-defined and wet etched. A titanium/gold(Au) layer is then deposited on the track area as a conductive layer andinterconnecting aluminum wires are ultrasonically bonded to the goldlayer.

The ferrite substrate typically used in this process generally contains5,000-6,000 pores/mm² with pore sizes which range from approximately 0.5micrometers up to approximately 5.0 micrometers. However, the depositionof alumina, nickel-iron and titanium layers on this porous substratedoes not cover all of the pores. In the gap wet-etching step, thealuminum layer is etched with an etchant such as phosphoric acid. It hasbeen found, that some of the etchant remains trapped in the ferritepores when the substrate is subsequently covered with the goldconductive layer. Reaction between the trapped etchant and the firstalumina layer overlying the ferrite substrate generates local internalpressure which pushes the upper layer films to form bubbles. The trappedgas eventually escapes creating a tiny hole at the center. The bubbleswhich are formed may also thereafter collapse as a result of theescaping gas, thereby forming "rosettes". The formation of "rosettes" inthe MR head track areas causes the track resistance to change andinduces failure due to electromigration. Such "rosettes" are a seriousproblem which becomes even more acute as track density increases on suchMR heads.

Moreover, in the ultrasonic wire bonding process previously described,the alumina layer undergoes chemical changes through the transfer ofultrasonic energy. These changes promote preferential migration of iron(Fe) from the nickel-iron film toward the nickel-iron/first aluminainterface. This preferential migration induces the formation of oxidiciron (FeO) at this interface. Such complex chemical mechanisms weakenthe adhesion between the nickel-iron film and the first layer ofalumina, which results in film delamination at this nickel-iron/aluminainterface during the wire bonding step.

Both the formation of "rosettes" and the undesired ultrasonic inducedfilm delamination affect the performance and yield of MR devicesmanufactured in accordance with the foregoing process. It is, therefore,highly desirable to eliminate or reduce the "rosette" formation and theultrasonic induced film delamination at the nickel-iron/aluminainterface.

Certain problems attendant to the rupture and the delamination ofcertain thin films in the processing and manufacture of MR devices havebeen recognized. U.S. Pat. No. 4,914,538 entitled "Magnetoresistive ReadTransducer", issued Apr. 3, 1990 proposes the use of a thin filmunderlayer in conjunction with a thin film overlayer formed of materialtaken from the group consisting of titanium, chromium (Cr), tantalum(Ta), zirconium (Zr), hafnium (Hf) and titanium tungsten (TiW) to reduceetchant penetration and resultant delamination of tungsten (W) films.The thin film underlayer or overlayer is described as having a thicknesswithin the range of 25-200 angstroms to prevent rupture and delaminationof the relatively porous tungsten films utilized in the devicedescribed. U.S. Pat. No. 4,931,892 for "Long Life Magnetoresistive Headof the Non-Shunt Bias Type", issued on Jun. 5, 1990 advocates the use ofa "sacrificial" material, such as titanium, in electrical contact withthe MR element to extend the useful life of the more "noble" NiFepermalloy portions of the structure. Suggested thicknesses for the"sacrificial" material are on the order of less than 200 angstroms andmaterials such as titanium, tin (Sn), aluminum (Al), zirconium andchromium are described. Neither of the techniques described in theforegoing patents has provided or suggested a satisfactory solution tothe undesirable formation of "rosettes" or delamination at thenickel-iron/alumina interface in the processing and manufacture of an MRelement.

It is with respect to these and other considerations that the presentinvention has evolved.

SUMMARY OF THE INVENTION

In general, the present invention proposes the formation of a barrier onthe first alumina surface of a structure used in manufacturing an MRdevice which is chemically inert to etchants and also remains stableduring the ultrasonic wire bonding process. The barrier formationprocess preferably results in an approximately 35 angstrom thickaluminum-titanium oxidic compound formed on the first alumina surface.The aluminum-titanium oxidic compound acts as a barrier to preventetchant from entering into the pores of the ferrite substrate during thesecond alumina layer etching step and thus eliminates or minimizes"rosette" formation. The aluminum-titanium oxidic compound also acts asa passivation layer which does not undergo chemical changes due to theapplication of ultrasonic energy during wire bonding and thus preventsfilm delamination during device subsequent processing. Forming thebarrier layer is particularly useful when processing a generally poroussubstrate having a layer of aluminum oxide formed thereon and an ironcompound layer in an overlying relationship thereto, in which case theprocess includes the steps of forming an aluminum-titanium oxidiccompound layer on the aluminum oxide layer. The iron compound layer isthen formed on the aluminum-titanium oxidic compound layer.

Another aspect of the invention relates to a thin film device having atleast an aluminum oxide layer and an iron compound layer in an overlyingrelationship, in which an aluminum-titanium-oxidic compound layer isinterposed between the aluminum oxide layer and the iron compound layer.

In accordance with another aspect of the present invention, a method offorming a thin film device involves the steps of providing a substrateand establishing a first alumina layer on a major surface thereof. Analuminum-titanium oxidic compound layer is formed on the first aluminalayer and an iron compound layer is additionally established on thealuminum-titanium oxidic compound layer. A first titanium layer isadditionally formed on the iron compound layer and portions of thetitanium and iron compound layers are selectively removed to define anaperture or gap, therein. A second alumina layer is established withinthe gap and a conductive layer overlying the first titanium layersurrounding the second alumina layer is thereafter formed.

The features and objects of the present invention and the manner ofattaining them will become more apparent and the invention itself willbe best understood by reference to the following description of apreferred embodiment thereof taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b are simplified, partial, cross-sectional viewsillustrative of a prior art thin-film structure and process flowsequence in which, for example, an aluminum oxide (or alumina) layeroverlies a porous substrate (such as ferrite) and upon which an ironcompound, magnetoresistive layer (such as NiFe) is formed with atitanium overcoat.

FIG. 2a is a simplified, partial, cross-sectional view illustrative ofthe prior art thin-film device structure of FIGS. 1a and 1b, showing anadditional alumina gap layer formed within an aperture defined in afirst titanium layer and the iron compound layer and utilizing, forexample, a second titanium layer and a gold layer as a conductive layer.

FIG. 2b is a follow on, simplified, partial, cross-sectional view of theprior art thin film device of FIG. 2a, illustrating the attachment of aconductive wire to the conductive layer by means of, for example, anultrasonic wire bonding process, and further illustrating thepreferential migration of iron from the nickel-iron film toward thenickel-iron/first alumina layer interface to form iron oxide (FeO)thereat, to result in film delamination during the wire bonding process;

FIG. 2c is an additional follow on, simplified, partial, cross-sectionalview of the prior art thin film device of FIG. 2b showing the formationof an iron oxide region at the nickel-iron/alumina interface due to thetransfer of ultrasonic energy in the wire bonding process.

FIGS. 3a-3d are simplified, partial, cross-sectional views illustrativeof the prior art thin film device structure of FIGS. 1a, 1b and FIGS.2a-2c in which a pore within the porous substrate is shown in FIG. 3a,which pore traps an etchant during a subsequent etching of the secondalumina layer due to the inadequate coverage of the first alumina andiron compound layers as shown in FIG. 3b, allowing the etchant to causea bubble to be formed in the layers overlying the pore as shown in FIG.3c which collapses in the region overlying the pore to form a "rosette"as shown in FIG. 3d.

FIGS. 4a-4j are partial, cross-sectional views illustrative of amagnetoresistive device and barrier formation process in accordance withthe present invention in which an aluminum-titanium oxidic compoundlayer is preferentially formed at the interface of the first aluminalayer/iron compound layer interface to serve as both an etching barrierfor the first alumina layer during the gap etching step of the secondalumina layer to prevent "rosette" formation and as a passivation layerto prevent the first alumina surface from being modified by the transferof ultrasonic energy in the wire bonding process to thereby reduce thefilm delamination at the first alumina layer/iron compound layerinterface. FIGS. 4a-4j also show the process flow for constructing amagnetoresistive read head of the non-shunt bias type.

DETAILED DESCRIPTION

With reference to FIG. 1a, a prior art structure 10 is shown. The priorart structure 10 comprises a substrate 12 presenting a porous surface 14upon which a first alumina layer 16 is deposited or formed. The firstalumina layer 16 presents an alumina surface 18 as shown.

The substrate 12 may be conveniently formed of ferrite, ceramic or otherpolycrystalline materials. Typically, when using a ferrite substrate 12,the substrate contains 5,000-6,000 pores/mm² with pore sizes varyingfrom less than 0.5 micrometers up to approximately 5.0 micrometers. Thefirst alumina layer 16 may vary from 1,400 angstroms to 1,800 angstromsin thickness. However, the deposited first alumina layer 16 does notadequately cover the pores on porous surface 14 of substrate 12 whichcan lead to the trapping of etchant within the pores as will be morefully described hereinafter.

Referring additionally now to FIG. 1b, the prior art structure 10 ofFIG. 1a is shown with an additional structure 20 added thereto. Theadditional structure 20 comprises a nickel-iron (NiFe) film 22 depositedupon the alumina surface 18 of the structure 10. The nickel-iron film 22presents a NiFe surface 24 upon which there is deposited a firsttitanium (Ti) film 26 presenting a first Ti surface 28.

The nickel-iron film 22 forms the MR element of the device to bedescribed more fully hereinafter. The nickel-iron film 22 is preferablydeposited to a thickness of between 680 angstroms to 800 angstroms whilethe first titanium film 26 may preferably be on the order of 200angstroms thick. The deposited nickel-iron film 22 also does notadequately cover first alumina layer 16 which is adjacent to the poreson porous surface 14 of substrate 12, allowing the etchant to enter andbecome trapped within such pores. The nickel-iron film 22 is alsoetchable in phosphoric acid while the titanium of the first titaniumfilm 26 is not etchable in the acid. The first titanium film 26deposited on top of the nickel-iron film 22 acts as a barrier to preventthe NiFe material from etching in the subsequent etching process of thesecond gap layer of alumina as will be more fully described hereinafter.

Referring additionally now to FIGS. 2a, 2b and 2c, a magnetoresistive(MR) head 40 is shown. The magnetoresistive head 40 is shown constructedupon the structure 10 and the additional structure 20. For purposes ofdescribing the problems attendant the structure and processing ofmagnetoresistive head 40, an interface 30 is defined as the intersectionbetween the alumina surface 18 of the first alumina layer 16 and thenickel-iron film 22.

A second alumina layer 32 is patterned onto and formed within theadditional structure 20 in a gap region of magnetoresistive head 40. Thesecond lumina layer 32 contacts the first alumina layer 16 within thegap region. The gap region is formed by photolithographic means withinadditional structure 20. Following photo definition of the gap region,the first titanium film 26 and the nickel-iron film 22 are ion milled toform the gap region. The second alumina layer 32 may be approximately6,800 angstroms to 9,300 angstroms in thickness depending on the uses towhich the MR head 40 will be put. Process control of the deposition forsecond alumina layer 32 is such that its etching rate in phosphoric acidis approximately two times that of the first alumina layer 16.

A second titanium film 34 is deposited on the first Ti surface 28. Thesecond titanium film 34 presents a second Ti surface 36 upon which isfurther deposited a gold (Au) film 38. The conductive layer comprisingthe second titanium film 34 and gold film 38 are photolithographicallydefined. Thereafter, phosphoric acid etching of second alumina layer 32takes place within the gap of region of the MR head 40. In this etchingstep, etchant is trapped within the pores of substrate 12 due to therelatively poor coverage of these local areas by the nickel-iron film 22and first alumina layer 16.

In the deposition of the conductive layer comprising the second titaniumfilm 34 in conjunction with the gold film 38, typical thicknesses areapproximately 5,000 angstroms for the gold film 38 and approximately 200angstroms for the second titanium film 34. The 200 angstrom thicktitanium deposition of the second titanium film 34 prior to thedeposition of the gold film 38 enhances film adhesion. During thedeposition process, the substrate 12 is heated to 90° celsius. Thistemperature is, unfortunately, also favorable for inducing a reactionbetween the trapped phosphoric acid etchant and the first alumina layer16. The problems attendant to this trapped etchant will be more fullydescribed hereinafter.

Referring now specifically to FIGS. 2b and 2c, ultrasonic bonding of awire 39 to the gold film 38 by means of a bond 37 is shown. The wire 39,which may comprise aluminum, is ultrasonically bonded to the gold film38 as necessary to effectuate the bond. Concurrently, ultrasonic energyis transferred from the transducer of the wire bonder to the underlyingalumina surface 18 of the first alumina layer 16, and that ultrasonicenergy induces changes within the first alumina layer 16 at theinterface 30 with the nickel-iron film 22. These changes promotepreferential migration of iron from the nickel-iron film 22 toward theinterface 30 to form iron oxide and unintentionally increase the volumeof the interface 30. Such complex mechanisms weaken the adhesion at theinterface 30 between the nickel-iron film 22 and the first alumina layer16 resulting in film delamination at the interface 30 as a typical andunintended consequence of the wire bonding step.

Referring additionally now to FIGS. 3a-3d, an illustration of thedifficulties encountered when the etchant is trapped within the pores ofsubstrate 12 is shown. In the description of the structure illustratedin FIGS. 3a-3d, like structure to that above described with respect toFIGS. 1a-1b and 2a-2c is like numbered and the foregoing descriptionthereof shall suffice herefor.

As illustrated in FIGS. 3a-3d, the substrate 12 contains a number ofpores varying in size from approximately less than 0.5 micrometers toapproximately 5.0 micrometers. An example of such, a single pore 42, isshown. As previously described, phosphoric acid etching of the gapregion necessary to deposit the second alumina layer 32 (as shown inFIGS. 2a-2c), leaves some phosphoric acid, or other etchant 44 withinthe pore 42. During the deposition of second titanium film 34 (as shownin FIGS. 2a-2c), the substrate 12 is heated to 90° celsius. Thistemperature is also favorable for initiating a chemical reaction betweenthe trapped etchant 44 and the first alumina layer 16. Such reactiongenerates local internal pressure which pushes the upper layer of theoverlying films to form bubbles in the region 46. The gas contained inthe bubbles eventually escapes creating a tiny hole at the center of thebubble, whereupon the bubble collapses as a result of the escape of thegas. The collapsed bubble in the region 46 creates a rosette 48. Theformation of rosettes 48 in the track areas of an MR head undesirablyalters the track resistance and induces failure due to electromigration.

It has been discovered that, in order to reduce or eliminate rosette 48formation and the ultrasonically induced film delamination at theinterface 30 between the nickel-iron film 22 and the first alumina layer16, the formation of a barrier on the alumina surface 18 of the firstalumina layer 16 at the interface 30 must be established. The barriermust be relatively chemically inert to etchants used in the thin filmdevice processes and also remain stable under ultrasonic wire bondingconditions.

Referring now to FIG. 4a, an improved structure 50 for fabrication of anMR transducer or head, is shown. The improved structure 50 comprises asubstrate 52 presenting a porous surface 54 upon which is deposited afirst alumina layer 56. The first alumina layer 56 presents a firstalumina surface 58. The substrate 52, which may be ferrite, ceramic orother polycrystalline material generally has between 5,000 to 6,000pores/mm² on the porous surface 54 if ferrite is used. The first aluminalayer 56, which may be between 1,400 to 1,800 angstroms in thickness,does not adequately cover the pores of the porous surface 54 to preventetchant utilized in subsequent processing steps from entering the poresand becoming trapped.

Upon the first alumina surface 58 of the first alumina layer 56, abarrier layer 60 is formed in a manner which will be more fullydescribed hereinafter. The barrier layer 60 comprises analuminum-titanium oxidic compound (Al_(x) Ti_(y) O_(z)) and has athickness of less than 100 angstroms, preferably on the order ofapproximately 35 angstroms. Overlying the barrier layer 60, anickel-iron film 62 is deposited presenting a NiFe surface 64. A firsttitanium film 66 is then further deposited on the NiFe surface 64presenting a first Ti surface 68. The combination of the substrate 52with the first alumina layer 56 is shown to be a first structure 70while the combination of the nickel-iron film 62 and the first titaniumfilm 66 comprises a second structure 72 separated by a barrier layer 60.

The nickel-iron film 62 and the first titanium film 66 of the structure72 are generally deposited in a sputter-deposition system in which thebarrier layer 60 is simultaneously formed. The tooling and the chamberwall of the sputter-deposition system used in the fabrication of an MRhead in accordance with the present invention become coated over timewith an alternate layer of titanium, nickel-iron, titanium, nickel-ironetc. In this manner, titanium always remains at the top layer of thechamber wall and on the tooling surface at the end of each cycle of thetitanium/nickel-iron deposition process. Prior to the deposition ofnickel-iron film 62, a pre-sputter etching of first alumina surface 58is performed in the sputter-deposition system where a DC bias is appliedto the tooling surface as well as the first alumina surface 58. Thesputtered species from the tooling are then redeposited onto the firstalumina surface 58 which is also simultaneously sputter etched bysputtering gas. Under the controlled process parameters of thispre-sputter etching step, the redeposition of titanium on the firstalumina surface 58 will occur. During the sputter etching of the firstalumina surface 58, oxygen is preferentially sputtered away from thefirst alumina surface 58 resulting in the formation of an unstablealuminum sub-oxide which promotes the reactions which take place betweenthe redeposited titanium and the sputtered alumina surface 58 to formthe barrier layer 60. This reaction results in the formation of thealuminum-titanium oxidic compound of the layer 60 with a thickness ofless than 100 angstroms and preferably approximately 35 angstroms, onthe first alumina surface 58.

This aluminum-titanium oxidic compound of the layer 60 is not etchablein phosphoric acid and does not chemically change upon application ofultrasonic energy in a subsequent wire bonding step. The presence of thealuminum-titanium oxidic compound barrier layer 60 at the interfacebetween the nickel-iron film 62 and the first alumina layer 56 acts asboth an etching barrier for first alumina layer 56 during the gap regionetching process (thus preventing "rosette" formation), and also as apassivation layer to prevent the first alumina surface 58 from beingmodified by the effect of ultrasonic energy applied in the subsequentwire bonding process (thus reducing film delamination at the interfacebetween the nickel-iron film 62 and the first alumina layer 56). As willbe more fully described hereinafter, additional methods for forming analuminum-titanium oxidic compound barrier layer 60 may be used which aresimilarly effective in preventing rosette formation and establishing apassivation layer between nickel-iron film 62 and first alumina layer56.

Referring additionally now to FIG. 4b, subsequent processing steps forthe improved structure 50 are shown. Photoresist 74 is patterned uponthe first Ti surface 68 to form the gap region 76. Depending on thedesired structure for the MR head manufactured in accordance with thepresent invention, the width of the gap region 76 established betweenthe patterned photoresist 74 may vary between 200 to 430 micrometers.

Referring additionally now to FIG. 4c, a subsequent processing step isshown. Portions of the first titanium film 66 and the nickel-iron film62 are removed within the gap region 76 to form an aperture, or gap 78through the second structure 52a shown. The gap 78 may be formed by ionmilling of the combined nickel-iron film 62 and overlying first titaniumfilm 66 to essentially expose the first alumina surface 58 of the firstalumina layer 56 within the gap 78. As shown in FIG. 4d, the photoresist74 is then stripped away leaving the first Ti surface 68 of the firsttitanium film 66 exposed.

Referring additionally now to FIG. 4e, subsequent processing results ina second alumina layer 80 being deposited upon the first Ti surface 68as well as the first alumina surface 58 of first alumina layer 56 withinthe gap 78. The second alumina layer 80 presents a second aluminasurface 82 having a recess 84 therein in the area overlying gap 78. Thesecond alumina layer 80 which may have a thickness of between6,800-9,300 angstroms. The recess 84 is formed by a controlleddeposition such that the etching rate of the second alumina layer 80 byphosphoric acid when forming the recess 84 is approximately two timesthat of first alumina layer 56.

Referring additionally now to FIG. 4f, an additional photolithographystep is shown in which photoresist 86 is patterned upon the secondalumina surface 82 of the second alumina layer 80 and in the recess 84thereof. Patterning photoresist 86 above the recess 84 of the secondalumina layer 80 results in the formation of an opening 90 within thephotoresist surface 88.

Referring additionally now to FIG. 4g in comparison to FIG. 4f,phosphoric acid etching of the second alumina layer 80 takes place. Inthis process step, the second alumina layer 80 is etched in phosphoricacid. As shown, the second alumina layer 80 is etched such that thefirst Ti surface 68 of the first titanium film 66 is exposedsubstantially surrounding gap 78. In this etching step, etchant will betrapped in the pores of substrate 52 due to the inadequate coverage bythe first alumina layer 56 and the nickel-iron film 62.

With reference now to FIG. 4h, a conductive layer of the improvedstructure 50 is added. A second titanium film 92, preferably ofapproximately 200 angstroms in thickness, is deposited upon the first Tisurface 68 of the first titanium film 66. As shown, the second titaniumfilm 92 also overlies the photoresist 86 at the photoresist surface 88and the opening 90 therein.

The second titanium film 92 presents a second Ti surface 94 upon whichis preferably deposited an approximately 5,000 angstrom thick gold film96. The gold film 96 presents a gold surface 98 thereof. The gold film96 also overlies the second titanium film 92 at the second Ti surface 94overlying photoresist 86 as shown.

The 200 angstrom thick second titanium film 92 deposited prior to thedeposition of the gold film 96 is utilized to enhance the film adhesionto the first Ti surface 68 of the first titanium film 66. During thedeposition process, the substrate is heated as previously described toapproximately 90° celsius.

Referring additionally now to FIGS. 4i and 4j, the photoresist 86 isremoved (as shown in FIG. 4h) and with it those portions of the secondtitanium film 92 and the gold film 96 lying thereover. A wire 100, whichmay comprise aluminum, is thereafter ultrasonically attached to the goldsurface 98 of the gold film 96, forming a bond 102.

By means of aluminum-titanium oxidic compound barrier layer 60 formedbetween first alumina layer 56 and nickel-iron film 62, undesired"rosette" formation and film delamination is significantly reducedand/or eliminated. The barrier layer 60 may be produced in the mannerpreviously described, or, alternatively, by deposition of a film with aniron content on the first alumina surface 58 of the first alumina layer56. Prior to such film deposition, the first alumina surface 58 issputter etched and a thin film of titanium, approximately 35 angstromsthick would then be sputter deposited or evaporated onto the sputteretched alumina surface.

Alternatively, the barrier layer 60 may be produced using reactivesputter-deposition processes to build a layer of aluminum-titaniumoxidic compound on a non-alumina surface. In this process two targetmaterials, aluminum and titanium, would be co-deposited with an argongas (or other noble gas) having a predetermined oxygen content(approximately 5%). Utilizing such controlled process parameters and theproper target composition, an aluminum-titanium oxidic compound formingthe barrier layer 60 may be formed at the first alumina surface 58.

The barrier layer 60 of the improved structure 50 of the presentinvention will also find application in the processing and manufactureof thin film devices utilizing ferrite, ceramic or similar substratematerials having pores therein. The aluminum-titanium oxidic compoundlayer 60 is particularly useful in the manufacture of thin film deviceswhere there is presented an interface between an alumina layer and amaterial with an iron content such as nickel-iron film 62.

While there have been described above the principals of the presentinvention in conjunction with a specific apparatus, it is to be clearlyunderstood that the foregoing description is made only by way of exampleand not as a limitation to the scope of the invention.

What is claimed:
 1. A process for forming a barrier layer to thesubsequent occurrence of rosettes and film delamination duringprocessing of a porous substrate having a layer of aluminum oxide formeddirectly on said substrate, and having an iron compound layer in anoverlying relationship to said layer of aluminum oxide, comprising thesteps of:forming an aluminum-titanium oxidic compound barrier layerhaving a thickness of less than 100 angstroms directly on said aluminumoxide layer; and forming said iron compound layer directly on saidaluminum-titanium oxidic compound layer.
 2. The process of claim 1wherein said step of forming said aluminum-titanium oxidic compoundlayer is carried out by the step of:sputter etching said aluminum oxidelayer in the presence of a titanium and iron compound source.
 3. Theprocess of claim 1 wherein said step of forming said aluminum-titaniumoxidic compound layer is carried out by the steps of:sputter etchingsaid aluminum oxide layer; and forming a titanium film on said aluminumoxide layer.
 4. The process of claim 3 wherein said step of forming saidtitanium film is carried out by sputter deposition.
 5. The process ofclaim 3 wherein said step of forming said titanium film is carried outby evaporation.
 6. The process of claim 1 wherein said step of formingsaid aluminum-titanium oxidic compound layer is carried out by the stepof:reactive sputter depositing aluminum and titanium in the presence ofan inert gaseous atmosphere having an oxygen content.
 7. The process ofclaim 6 wherein said inert gaseous atmosphere comprises argon.
 8. Theprocess of claim 1 wherein said aluminum-titanium oxidic compound layerhas a thickness of about 35 angstroms.
 9. The process of claim 1 whereinsaid substrate comprises a ferrite.
 10. The process of claim 1 whereinsaid substrate comprises a ceramic.
 11. The process of claim 1 whereinsaid iron compound layer comprises nickel-iron.
 12. A process forforming a thin film device comprising the steps of: providing asubstrate;forming a first alumina layer directly on a surface of saidsubstrate; forming an aluminum-titanium oxidic compound barrier layerhaving a thickness of less than 100 angstrom directly on said firstalumina layer; forming an iron compound layer directly on saidaluminum-titanium oxidic compound layer; forming a first titanium layeron said iron compound layer; selectively removing a portion of saidfirst titanium layer and said iron compound layer to define an aperture;forming a second alumina layer within said aperture; and forming aconductive layer overlying said first titanium layer and surroundingsaid second alumina layer.
 13. The process of claim 12 wherein said stepof forming said aluminum-titanium oxidic compound layer comprises thestep of:sputter etching said first alumina layer in the presence of atitanium and iron compound source.
 14. The process of claim 12 whereinsaid step of forming said aluminum-titanium oxidic compound layercomprises the steps of:sputter etching said first alumina layer; anddepositing a titanium-oxidic compound on said first alumina layer. 15.The process of claim 12 wherein said step of forming saidaluminum-titanium oxidic compound layer comprises the steps of:sputteretching said first alumina layer; and evaporating a titanium oxidiccompound on said first alumina layer.
 16. The process of claim 12wherein said step of forming said aluminum-titanium oxidic compoundlayer comprises the step of:reactive sputter depositing aluminum andtitanium in the presence of an inert gaseous atmosphere having an oxygencontent.
 17. The process of claim 12 wherein said step of forming saidiron compound layer is carried out by deposition of nickel-iron.
 18. Theprocess of claim 12 wherein said step of forming said first titaniumlayer is carried out by deposition of titanium.
 19. The process of claim12 wherein said step of selectively removing a portion of said firsttitanium layer and said iron compound layer comprises the stepsof:defining said aperture on said first titanium layer; and removingsaid first titanium layer and said iron compound layer within saiddefined aperture.
 20. The process of claim 19 wherein said step ofdefining said aperture is carried out by patterning photoresist on saidfirst titanium layer to define said aperture.
 21. The process of claim20 further comprising the step of:stripping off said photoresistsubsequent to said step of selectively removing said portion of saidfirst titanium layer and said iron compound layer.
 22. The process ofclaim 19 wherein said step of selectively removing said portion of saidfirst titanium layer and said iron compound layer is carried out by ionmilling said first titanium layer and said iron compound layer withinsaid aperture.
 23. The process of claim 12 wherein said step of formingsaid second alumina layer comprises the steps of:depositing said secondalumina layer within said aperture and overlying said first titaniumlayer; defining a portion of said second alumina layer overlying saidaperture; and removing a portion of said second alumina layersubstantially surrounding said defined portion thereof at a positionoverlying said first titanium layer.
 24. The process of claim 23 whereinsaid step of defining a portion of said second alumina layer is carriedout by patterning photoresist on said second alumina layer generallyoverlying said aperture.
 25. The process of claim 23 wherein said stepof removing a portion of said second alumina layer comprises the stepof:etching away said portion of said second alumina layer substantiallysurrounding said defined portion thereof overlying said first titaniumlayer.
 26. The process of claim 25 wherein said step of etching away iscarried out by means of phosphoric acid.
 27. The process of claim 12wherein said step of forming said conductive layer comprises the stepsof:depositing a second titanium layer overlying said first titaniumlayer substantially surrounding said aperture; and depositing a goldlayer overlying said second titanium layer.
 28. The process of claim 12further comprising the step of:forming an electrical contact to saidconductive layer.
 29. The process of claim 12 wherein said step offorming said conductive layer includes the step of:bonding a wire leadto said conductive layer.
 30. The process of claim 29 wherein said stepof bonding a wire lead is carried out by ultrasonically bonding analuminum wire to said conductive layer.